Ga0.47In0.53As has been used to make fast (rt < 1 ns), photodiodes with low dark current ( A) and good quantum efficiency (ηQext > 50 percent over the entire m region of the optical spectrum). The physical properties related to the crystal growth and carrier transport are discussed in this paper in terms of both the design and the operating characteristics of detectors fabricated from this ternary alloy. The results of our work show that Ga0.47In0.53As is a material well-suited to several important semiconductor device applications. A comparison to other semiconductor photodiodes shows that Ga0.47In0.53As is one of the most sensitive detectors available in the m wavelength region. One can expect repeater-free transmission in excess of 150 km at 100 Mbits . s-1using these detectors in a digital optical fiber link at the 1.55 μm low-loss ( dB . km-1) low-dispersion transmission window.